Re: Data model storage optimization

How many rows in average per partition?

Let me get this straight : You are bifurcating your partitions on either email or username , essentially potentially doubling the data because you don’t have a way to manage a central system of record of users ?

I would do this: (my opinion)
Migrate to a single sign on System that uses one or the other. Map and migrate your data to use a singular record as “identity”.

I know that seems painful but I _hate_ perpetuating bad design because someone , in the past, presence , or future chooses to not solve the problem but get around it.

This is not a storage optimization problem - it’s a data architecture problem.